Elimination of chattering or hum in alternating-current electromagnets



C. L. PER RY 7 June 11, 1929.

ELIMINATION OF CHATTERING OR HUM IN ALTERNATING CURRENT ELECTROMAGNETS Filed July 10, 1925 Patented June 11, 1929.

' UNITED STATES v 1,711,241 PATENT OFFICE.

CHARLES L. PERRY, 0F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELIMINATION OF CHATTERING OR HUM IN ALTERNATING-CURRENT ELECTROMAG- NETS.

Application filed July 10, 1925. Serial No. 42,772.

My invention is directed to improvements whereby the customary chattering or characteristic hum of an electromagnet when operated on alternating current circuits is eliminated, and also whereby the energy required to maintain the magnetic movable element of the electromagnet in the attracted position is materially reduced.

Various expedients have heretofore been proposed and adopted to eliminate the characteristic chattering or hum of an electromagnetic device when operated on an alternating current circuit. Pole shaders are most frequently employed for this purpose and these are more or less satisfactory de pending on the accuracy of the fit of the contacting surfaces of the magnetic movable element with the pole or poles of the electromagnet, and also depending somewhat on the tendency of the magnetic movable element to assume the unattracted position due to the load thereon. That necessitates a substantial energization of the electromagnet. Expedients have been adopted to insure a good fit of the said contacting surfaces, such as self aligning surfaces, and the like. However, at best, these expedients are frequently only partially successful and the characteristic objectionable hum is heard. Furthermore, pole shaders, self-aligning contacting surfaces and the like are objectionable in that special constructions are necessary and such constructions are expensive.

In accordance with my invention, the objectionable chatter or hum is eliminated by rectifying the alternating current by means of a kenotron or other suitable rectifying de vice so that the current supplied to the winding of; the electromagnet is unidirectional. One of the important advantages of the invention is that not only is the objectionable chattering or hum eliminated but also the energy required to maintain the magnetic movable element of the electromagnet in the attracted position is materially reduced. There is ordinarily no objection to operating the electromagnetic device with alternating current so it is preferable, although not necessary, to operate the device with alternating current and then maintain the device in the operated position with the rectified current since the rectifying device or. devices need thus be of relatively small capacity.

For a better understanding of the invenplunger type and as having an operating v winding 12 and a maintaining winding 13. However, I would have it understood that the invention is not necessarily limited to plunger type electromagnetic devices, since the invention is generally applicable to electromagnetic devices having a magnetic movable element operated in res onse to the energization of the winding 0 the electromagnet. A familiar type of electromagnetic device to which the invention is applicable is the pivoted armature type of electromagnetic switch in which the armature makes abutting engagement with pole pieces of the electromagnetic structure of the device when the electromagnet winding is energized. I would also have it understood that the invention is not necessarily limited to an arrangement in which one winding is provided for operating the device and another winding is provided for maintaining the device in the operated position, since those skilled in the art will readily appreciate from an understanding of the invention that the invention is likewise applicable to single winding electromagnetic devices in which the winding serves to not only operate the device, but also to maintain the device in the operated position. It will therefore be understood that the present arrangement has been shown merely for the purpose of illustration of the principles of the invention.

The electromagnetically operated switch 10 is of the type which is disposed tochatter or produce the characteristic hum when the same is maintained energized from the alternating current source of supply 11. In order to eliminate this chattering or characteristic hum, the thermionic rectifying devices 14 and 15 have been provided to rectify the alternating current of the source of supply 11 and supply a unidirectional current to maintain the switch '10 in the operative position. These rectifying devices are preferably of the kenotron type and although it is not necessary that they be connected as shown, nevertheless the arrangement shown p in an evacuated container 18. The kenotron has been shown in diagrammatic form, since this is a well known device and it is therefore deemed to-be unnecessary to illustrate and describe thedeta-ils ofconstruction and arrangement.

The step down transformer 19 is provided for supplyinga reduced potential to the maintaining winding 13 of the contactor 10 through the kenotrons 14 and 15. This transformer is desirable, although not strictly necessary,-

since the kenotrons maybe connected and employed so as to rectify the alternating current of the source 11 directly without the interposition of the step down transformer. However, the provision of the transformer makes a convenient arrangement in that the heated filaments or cathodes of the kenotrons may be connected across a few turnsof the secondary of the transformer and thereby supply a relatively low potential for the cathode clrcuit.

mally closed auxiliary switch 20 and a normally open auxiliary switch 21, the arrangement being such that with the contactor in the open position as shown, the winding 12 will be energized through the auxiliary switch 20, and'when the contactor has been closed, the auxiliary switch 20. will open its contacts and by reason of the fact that the auxiliary switch 21 has been closed duringthe closing of the contactor, the maintaining winding 13 will 'be energized through the kenotrons by unidirectional current.

The operation of my invention as thus constructed and arranged and with the parts in their respective positions shown in the drawing, is as follows: In order to energize the contactor 10 to close, the master or controlling switch 22 is closed, thereby energizing. the winding 12 of the contactor 10 directly'across the the source of supply 11.. The contactor will be thus energized to close its main switch contacts 23, and when the contactor has practicallv completed its closing operation, the auxiliary switch 20 will be automatically opened and the auxiliary switch will he automatically closed. The opening of the auxiliary switch 20 will deenergize the operating winding 12 and the closing of the auxiliary switch 21 will energize the maintaining winding'13 through the kenotrons 14 and 15. As before explained, these kenotrons will rectify both pf the half cycles of the alternatingcurrent source of supply and produce a unidirectional current which will have the prac-- tical effect of a continuous current so thatthe characteristic chattering or hum of the eon-'7 .tactor 10 is eliminated. The-kenotron 18 will gy were taken directly from the alternating current source of supply. Thisis of impor tance, particularly inlarge electromagnetic devices, since in such devices asubstantial energization must be maintained. in order to minimize as much as possible the chattering or characteristic hum and this produces an objectionable heating-of the winding device and furthermore, is wasteful of power. \Vhen the pilot switch 22 is opened, the electromagne'tlc switch 10 is deenergized and per- ;mitted to assume its normal open position,

the various parts then being in their re spective the contactor 10 are completely disconnected from the supply circuit. The contactor 10 is provided with a nor- .by Letters Patent of the United States, isE

What I claim as new and desire to secure 1.- In combination, an alternating current source of supply, an electromagnetically operpositions shown in the drawings. .fWhen this switch 22 is opened, the transformer 19' as well as the kenotrons 14 and 15 and.

ated 'device having an electromagnet connected to be energized with alternating. current from said source and including a magnet1c movable element which is opera ted upon the energizatlon of said electromagnet from said source, the said electromagnet being disposed to chatter or hum when alternating current energization thereof is maintained,

rectifying means for changing the current of said source to a unidirectional current source of supply for said electromagnet, and switch mechanism for changing the connection of the electromagnet after the initial energization thereof from said source to said rectifymg means and thus reduce the energy necessary to maintain said device in the operated.

position thereof and prevent the said chattering or hum.

2. In combination, an alternating current source of supply, an electromagnetically operated device having an electromagnet connected to be energized with alternating cur rent from said source and including a magnetic movable element operated thereby upon the energization of the electromagnet from said source, the said'electromagnet being disposed to chatter or hum when alternating current energization thereof is maintained,

means for rectifying both half cycles of the said alternating current source to provide a unidirectional current source of supply for said electromagnet, and switch mechanism for changing the connection of the electromagnet after the initial energization thereof from said source to said rectifying means and thus reduce the energy necessary to maintain said device in the operated position there of and prevent the said chattering or hum.

3. In combination, an electromagnetically operated device having an electromagnet, including a magnetic movable element operated thereby upon the energization of the electromagnet, an alternatin current source of supply, thermionic recti ying means interposed between the said source and said electromagnet to supply a unidirectional energizing current to the electromagnet, and switch mechanism and connections whereby the said electromagnet is energized initially from said source to operate said element and the element is maintained in operated position by the unidirectional current supplied by said rectifying means to thereby reduce the energy necessary to maintain said device inthe operated position thereof and prevent the chattering or hum of said electromagnet.

4. In combination, an electromagnetically operated device having a winding and a magnetic movable element, an alternating current source of supply, thermionic rectifying means for changing the alternating current of said source to a unidirectional current, and means including switch mechanism and electrical connections through which the said winding is energized initially from said source to effect operation of said device and then the'said winding is energized through said rectifying means to maintain the device v in the operated position, whereby the chattering or hum of said device which would occur if the device were maintained energized by the alternating current of said source is prevented and the current necessary to maintain said device in the operated position is reduced.

5. In combination, an alternating current source of supply, a movable magnetic member, an electromagnet having an operating winding for magnetically operating said member from one position to another position upon the energization of said winding from said alternating current source of supply and a holding winding for magnetically holding said member in said other position, and alternating current to direct current rectifying means connected between said alternating current source of supply and said holding winding for supplying unidirectional energizing current to said holding winding.

6. In combination, an alternating current source of supply, an alternating current to direct current rectifying device, an electromagnet having two windings and a movable magnetic member, and switching mechanism and electrical connections through which one of said windings is energized directly from said alternating current source of supply for magnetically operating said magnetic member from one position to another position and the other of said windings is energized from said alternating current source of supply throu 11 said rectifying device for magneticaIly holding said magnetic member in said other position.'

7. In combination, an alternating current source of supply, an alternating current to direct current rectifying device, an electromagnet having an operating winding connected to be energized from said alternating current source of supply and a holding winding connected to be energized from said rectifying device, a movable magnetic member arranged to be operated from one position to another position under the magnetic influence of said operating winding and to be held magnetically in said other POSI- tion by said holding winding, and switching means associated with the magnetic member for deenergizing the operating winding when the magnetic member is held under the magnetic control of the holding winding and thereby reduce the energy consumption of the electromagnet.

In witness whereof, I have hereunto set my hand this 9th day of July, 1925.

CHARLES L. PERRY. 

